Rim-holding style tire changers are known. A typical rim-holding tire changer includes a chassis having a rotatable tabletop and a tower. A combination mount/demount head is supported by the tower. For example, the mount/demount head may be located at the distal end of a pivotable swing arm attached near the top of the tower. In other cases, the tower itself is tiltable toward and away from the tabletop. Various rim-holding style tire changers are manufactured by Hennessy Industries, Inc. and marketed under the trademark COATS®.
During a typical tire mounting procedure, the operator places a rim on the tabletop, secures the rim to the tabletop using radially-movable clamps, places a tire over the rim, mounts the tire by using the mount/demount head to force the bead of the tire over the rim, and then fills the air chamber of the tire with air to inflate the tire. In most cases, the previous tire must first be removed from the rim before installing a new tire. This procedure is described in detail in U.S. Pat. No. 5,623,981, which is incorporated by reference herein in its entirety. It is important that the rim be securely held during this process as it requires a considerable amount of force to mount and demount the tire from the rim. Additionally, it is also important that this be accomplished in a manner that does not damage the rim.
The clamps are typically attached to respective clamp carriers located on the tabletop. The operator controls inward and outward movement of the clamp carriers in a radial direction to secure or release the rim, as desired. The clamps are generally constructed from steel or a similar hard metal and formed so that they can be used in two ways, either by clamping the outer periphery of the rim or by clamping an inside surface of the rim. The clamps often have serrations on their respective outer surfaces for engaging the inside surface of the rim and a cupped surface, or claw, on the inside of the clamp for holding the rim from the outside. With existing rim-holding tire changers, it is not uncommon for there to be some amount of rotational slippage of the rim relative to the clamps during the mount/demount procedure. The rotational slippage is undesirable in that it can lead to possible damage to the rim.
Inside clamping of the tire rim presents various considerations that may be relevant. For example, tire rims often have a “conical” taper on the rear inside surface where the rim is held for tire removal and replacement. In many cases, road grime and oil may have accumulated on this tapered surface. Because the force used to hold the rim in place is based on a frictional connection, the road grime and oil may cause the wheel to move upward and off the clamps. In addition, the increased force required to remove performance type tires from the rim of the wheel can cause the frictional connection to fail. If the rim becomes disengaged from the clamps, significant damage to the decorative surfaces of the rim can result. As expected, the varying amounts of damage that are possible can require that the rim of the wheel has to be repaired or replaced.
To remedy these issues, in some cases, manufacturers have provided a protective covering of plastic material to cover the clamp. Manufacturers have also provided rubber blocks that are compressed between the clamp and the inside surface of the wheel rim. However, the plastic covers and the rubber blocks may not effectively secure the rim unless it is clean and free of road grime and the like. Another option has been to put nylon booties over the clamps to protect the wheel rim, but this method suffers from the same issues noted above.
Additionally, it is known to provide a clamp for use in a rim-holding tire changer wherein resilient gripping plates are disposed between metal support plates such that first portions of the gripping plates engage the rim of the wheel during inside clamping operations and second portions of the gripping plates engage the rim of the wheel during outside clamping operations. For example, such a clamp is described in detail in U.S. Pat. No. 6,062,289, the entire disclosure of which is incorporated by reference herein, and which is assigned to the Assignee of the present invention.
The present invention recognizes and addresses the foregoing considerations, and others, of prior art constructions and methods.